The present invention relates to a method and apparatus for controlling a driving system of a packaging apparatus, and more particularly to a method and apparatus for controlling a driving system of a packaging apparatus in which when objects to be packaged are not supplied from a supplying device to a packaging apparatus main body, the driving system is controlled in accordance with an improved response characteristic in a manner such that operation of a film supplying device and a film cutting device are interrupted, thereby temporarily to avoid forming empty packaged portions.
In general, when manufacturing packaged products by a stretch packaging apparatus, a lateral pillow packaging apparatus and the like, a packaging film in the form of a continuous strip is withdrawn from a roll of film which is made up of an elongate film would around a reel. While being withdrawn, the strip packaging film is formed into a cylindrical shape, and objects to be packaged are supplied into the cylindrical packaging film at regular intervals one after another. Next, the objects to be packaged and the cylindrical packaging film are fed forwardly by a conveying device while remaining in such state. While being conveyed, the cylindrical packaging film is cut and sealed to form packaged products. Incidentally, such stretch packaging does not require a sealing operation.
In the above conventional method and apparatus, if the objects to be packaged are orderly supplied into the cylindrical packaging film one after another, generally problems do not occur. However, when the objects to be packaged are not supplied into the cylindrical packaging film for some reason, the above conventional method and apparatus have given rise to the following problems.
That is, in the stretch packaging apparatus, since the stretch film per se constituting a packaging film is easily stretchable, a pair of endless belts are provided along with sides of the feeding path in order to stably feed the stretch film and the objects inserted in the stretch film. The feeding force is generated by holding both sides of the object to be packaged by the pair of endless belts, with the film between the object and each belt. Therefore, if the objects to be packaged are not orderly supplied at regular intervals, the feeding force is not accurately transmitted to the objects to be packaged and the stretch film. This results in a failure to feed both the objects to be packaged and the stretch film at a predetermined speed or in a stoppage of feed thereof. However, during such feed failure, the strip stretch film still is continuously withdrawn from the roll of film.
As a result, the strip stretch film is slackened or wrinkled at the position where the withdrawn strip stretch film is formed into a cylindrical shape. If the object to be packaged and the cylindrical film are fed at a lower speed than the predetermined speed, the relative positions of the front and the rear of the object are displaced from regular or planned positions thereof. This results in the cutting device erroneously cutting the object to be packaged or in either the cutting device or an end sealing device contacting and holding the object to be packaged.
On the other hand, in the pillow packaging apparatus, since the strength of the packaging film to be used is relatively high, the above problem is avoidable. However, that portion of the packaging film where an object to be packaged is not inserted becomes an empty packaged portion. This represents a waste of the packaging film.
In the conventional method and apparatus, in order to solve the above problems, a driving member such as a roller for continuously withdrawing the strip packaging film from the roll of film is connected to a driving motor through a clutch brake, and a driving member such as an endless belt for feeding the packaging film which encloses the objects to be packaged is connected to a driving motor through a clutch brake. If an object to be packaged is not supplied, such driving members are disconnected from the driving motors by the clutch brakes, and the corresponding driving members are stopped temporarily.
However, a clutch brake naturally has an inferior response characteristic, and long use of such a clutch brake causes a clutch member thereof to wear away, thereby further degrading the response characteristic. Furthermore, the use of such clutch brakes complicates the driving mechanism and increases manufacturing costs.